A139435 - OEIS

%I #5 Mar 30 2012 18:51:00

%S 0,0,2,0,1,4,4,1,6,2,4,8,4,8,10,2,2,12,8,4,14,8,2,16,4,8,18,16,8,20,

%T 16,4,22,4,20,24,16,16,26,8,4,28,14,16,30,10,8,32,28,10,34,16,13,36,

%U 24,32,38,16,20,40,15,32,42,12,20,44,32,8,46,40,28,48,20,32,50,32,44,52,26,20

%N Largest m<n such that first terms of the Collatz trajectory of m sum up to n; a(n)=0 if no such m exists.

%C a(n) = 0 iff A139436(n) = 0; a(n) > 0 for n > 4;

%C a(n) <= A004523(n); a(A008585(n)) = A005843(n).

%H R. Zumkeller, <a href="/A139435/b139435.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CollatzProblem.html">Collatz Problem</a>

%H <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>

%e a(30) = 20: 30 = 20+10;

%e a(31) = 16: 31 = 16+8+4+2+1;

%e a(32) = 4: 32 = 4+2+1+4+2+1+4+2+1+4+2+1+4;

%e a(33) = 22: 33 = 22+11;

%e a(34) = 4: 34 = 4+2+1+4+2+1+4+2+1+4+2+1+4+2;

%e a(35) = 20: 35 = 20+10+5.

%Y Cf. A006370.

%K nonn

%O 1,3

%A _Reinhard Zumkeller_, Apr 21 2008